Electric power of a circuit is the rate at which work is done in maintaining the electric current in the circuit.

The equivalent resistance in series combination is

Two electric circuits $I$ and $II$ are shown in the figure.
$(i)$ Which of the two circuits has more resistance?
$(ii)$ Through which circuit does more current pass?
$(iii)$ In which circuit is the potential difference across each resistor equal?

What is the resistance of insulating materials?

Why should the melting point of a fuse wire be low?

$(a)$ State the commercial unit of electric energy and find its relation with its $SI$ unit.
$(b)$ The current through a resistor is made three times its initial value. Calculate how it will affect the heat produced in the resistor.
$(c)$ Find the increase in the amount of heat generated in a conductor if another conductor of double resistance is connected in the circuit,keeping all other factors unchanged.